Heat-exchanger having a multiplicity of coaxial cylinders



P. LECLERCQ Oct. 5, 1965 HEAT-EXCHANGER HAVING A MULTIPLICITY OF COAXIAL CYLINDERS 5 Sheets-Sheet 1 Filed May 10, 1963 P. LECLERCQ 3,209,819

HEAT-EXCHANGER HAVING A MULTIPLICITY 0F COAXIAL CYLINDERS Oct. 5, 1965 5 Sheets-Sheet 2 Filed May 10, 1963 P. LECLERCQ 3,209,819

HEAT-EXCHANGER HAVING A MULTIPLICITY 0F COAXIAL CYLINDERS Oct. 5, 1965 5 Sheets-Sheet 3 Filed May 10, 1963 Oct. 5, 1965 P. LECLERCQ 3,209,819

HEAT-EXCHANGER HAVING A MULTIPLICITY 0F COAXIAL CYLINDERS Filed May 10, 1963 5 Sheets-Sheet 4 Oct. 5, 1965 P. LECLERCQ 3,209,819 HEAT-EXCHANGER HAVING A MULTIPLICITY OF COAXIAL CYLINDERS Filed May 10, 1963 5 Sheets-Sheet 5 United States Patent 3,209 819 HEAT-EXCHANGER HAK ING A MULTIPLICITY 0F (IOAXIAL CYLINDERS Pierre Leclercq, Blvd. Jeanne dArc,

Douai, Nerd, France Filed May 10, 1963, Ser. No. 279,639 Claims priority, application France, May 11, 1962, 897,211, Patent 1,330,305; Feb. 25, 1963, 925,842 16 Claims. (Cl. 165155) This invention relates to heat exchanges.

In addition to tube or plate heat exchangers, other heat exchangers are known which have concentric or coaxial cylinders enclosing annular spaces in which alternate spaces contain one fluid to be cooled or heated while the intermediate spaces contain the cooling or heating fluid. This distribution is achieved by means of distribution chambers at each end of the heat exchanger.

Each chamber commonly has a casing with an inlet for one fluid and an outlet for the other fluid communicating with this casing on opposite sides of a partition. The fluids separated by the partition, are admitted to alternate spaces in the heat exchanger by way of passages or apertures suitably disposed in a plate lying at right-angles to the axis of the cylinders and abutting the ends thereof.

The principal drawback of such an exchanger is that no heat exchange takes place in the distribution chambers, the heat exchange being solely effected in the above mentioned annular spaces. v

For any given problem therefore, calculation of the heat-exchange parameter dimensions takes account of the dimensions of the cylinders only. The distribution chambers are a necessary addition and increase the resultant space occupied.

It is an object of this invention to provide a remedy for this disadvantage by causing the distribution chambers to play an effective part in the heat exchange, so that, for any one problem, the volume and weight of the exchanger are reduced compared with the exchangers produced heretofore.

It is a further object of this invention to provide a heat exchanger having a high efficiency than exchangers produced heretofore and occupying the same volume.

Furthermore, in the existing exchangers, each distribution chamber has a peripheral flange which is bolted to an identical flange fixed to the ends of the outer cylinder of the heat exchanger proper. The bolts used also secure the apertured plate in such a way that they hold not only the chambers to the plate but also hold the cylinders to the plate, the plate having concentric grooves cut in its internally facing surfaces to take lealcproof packings and the ends of the cylinders bearing against these packings.

This method of assembly has disadvantages since heat stresses cause distortion of the apertured plates, these tending to bulge at the center since they are secured only around their periphery. The inner cylinders can thus come away from the grooves and break contact with the packings, allowing the annular spaces to communicate with one another and the fluids to mix.

It is thus a further object of this invention to prevent or mitigate such distortion and to maintain leak-proof seals between the cylinders and distribution chambers, not only at the periphery of the exchanger but also at its center.

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Further, in existing heat exchangers, the concentric cylinders make contact only at their ends with the plate packings. The ability to remove, clean. and refit the cylinders is an important advantage in exchangers of this type. However, the cylinder ends are very vulnerable to damage during these operations. To maintain proper rigidity, one therefore has to true the ends be fore refitting. Apart from the time wasted and the cost of machining for this purpose the cylinders are reduced in length which results in an exchanger of poorer per formance.

A further object of this invention is to ensure constant rigidity notwithstanding dismantling, by protecting against damage those parts of the cylinders. which make contact with the packings.

These and other objects of the invention will be more clearly understood from the following detailed description of various forms of construction, in conjunction with the accompanying drawings, in which:

FIGURE 1 is a partial longitudinal section through one form of heat exchangers;

FIGURE 2 is a cross-section of the same exchanger, through the line 11-11 in FIGURE 1;

FIGURE 3 is a partial longitudinal section of an exchanger of a similar type, showing how the various parts of the exchanger may be held in position from the center along;

FIGURE 4 is a more detailed drawing showing an improved seal between the cylinders and a perforated cylinder-locatin g plate;

FIGURE 5 is a longitudinal section of an exchanger applied to a boiler;

FIGURE 6 is a partial longitudinal section, showing one particular form of construction of the perforated plates and distribution chambers;

FIGURE 7 is a cross-section along the line VIIVII marked in FIGURE 6; and

FIGURE 8 is a perspective drawing of a perforated plate of the type shown in FIGURES 6 and 7.

Referring to FIGURES 1 and 2, it will be seen that the heat exchanger comprises a plurality of concentric or coaxial cylinders 0, adjacent pairs enclosing annular spaces 1 to 11, and the central cylinder 0 enclosing an empty space.

Cylinders 0 engage with circular grooves 12 provided in two perforated plates 13 and 14. Externally of these plates 13 and 14 are fitted part-cylindrical extensions 15 and 16, which engage in plates 13 and 14 in the same way as the cylinders 0. The outer ends of these part cylinders 15 and 16 engage in circular grooves in two end plates 17 and 18, through the lower part of which pass inlets 19 and 20 for the fluids and through the upper part of which pass outlets 21 and 22, each of which may be tubular or laterally extending and mounted either singly or in pairs.

The spaces enclosed between plates 13 and 17 at one end and between plates 14 and 18 at the other end constitute distribution chambers, the purpose of which is to direct the fluids into different annular spaces.

From FIGURE 2 it will be seen that the part-cylinders 15 are circumferentially interrupted, with the exception of the central tube, and that two sets of radial partitions, 23 and 24, connect the upper parts of adjacent part-cylinders 15 in pairs, blocking off annular spaces 1, 3, 5, 7, 9 and 11, and the lower parts of the said part-cylinders in pairs, blocking off annular spaces 2, 4, 6, 8 and 10. The lower part of plate 13 contains bores 25 extending therethrough and lying in correspondence with annular spaces 2, 4, 6, 8 and 10, while bores 26 in the upper part of the said plate lie in correspondence with annular spaces 1, 3, 5, 7, 9 and 11. Finally, in these parts of the distributor lying between the two sets of partitions 23 and 24 defining an obtuse angle the plate 13 has bores 27 lying in correspondence with the annular spaces 1 to 11.

Cylinders are enclosed in a cylindrical jacket 28, which is likewise fitted into plates 13 and 14, this jacket having an expansion chamber 29. The part-cylinders 15 and 16 are likewise enclosed in cylindrical jackets 30 and 31, which constitute the casings of the distribution chambers and to which flanges 32 and 33 are Welded. Flanges 32 and 33 have holes through which pass bolts 34 and 35, and by which jackets 3t and 31 are secured to plates 13 and 14.

End plates 17 and 18, as well as plates 13 and 14, have a central hole which lies coaxially with the central cylinders 0, 15 and 16 and through which no fluid circulates. End plates 17 and 18 are constrained towards each other by means of a tie-rod 36 on which lock-nuts 37 and 38 are screwed against plates 13 and 14, and nuts 39 and 40 against end plates 17 and 18, respectively.

In the annular space 1, which lies between the outermost cylinder 0 and the jacket 28, are welded stay-rings 41 and 42, which are drilled and tapped to take two sets of bolts, 43 and 44, to enable the cylinders 0 and jacket 28 to abut tightly against plates 13 and 14.

Deflectors 45 and 46, the purpose of which is to direct the fluids along their proper paths, are fixed to plates 13 and 14, opposite fluid inlets 19 and 20, respectively.

Leak-proof packings for the cylinders 0 and the partcylinders 15 and 16 are fitted into the circular grooves in plates 13 and 14 and end plates 17 and 18. The radial partitions 23 and 24, welded to part-cylinders 15 and 16, are likewise introduced into radial grooves in the plates 13 and 14 and in end plates 17 and 18, and it is thus simple to provide a continuous seal, running from one circular groove to another by way of a radial groove. In this way, the staunchness obtained is far more reliable, since there is no break in the packings.

This heat exchanger operates as follows:

A first fluid A is admitted to the exchanger through inlet 19 and a second fluid B is admitted through inlet 20. Fluid A passes between each of the two sets of the lower partitions 23 and 24 (FIG. 2), traverses annular spaces 2, 4, 6, 8 and in the distributor to the upper partitions 23 and 24 and at the same time passes through plate 13, by way of passages 25 and 27, into annular spaces 2, 4, 6, 8 and 10 in the heat exchanger proper. Having flowed through these spaces lengthwise of the exchanger, fluid A passes through those bores in plate 14 provided opposite spaces 2, 4, 6, 8 and 10 and emerges between plate 14 and end plate 18 in the distribution chamber identical to the one already described, being finally discharged through outlet 21.

Fluid B is distributed between plate 14 and end plate 18 in spaces 1, 3, 5, 7, 9 and 11, by reason of partitions 23 and 24 which block off spaces 2, 4, 6, 8 and 10, and flows through spaces 3, 5, 7, 9 and 11 between cylinders 0 through passages 48 in plate 14. In the same manner as fluid A, but in the opposite direction, fluid B flows the length of the heat exchanger, passes through plate 13 and is discharged through outlet 22.

In all the annular spaces 1 to 11 between cylinders 0, helical dividers are fitted, their geometrical axis being that of the cylinders (in other words, the center line of tie-rod 36). In spaces 2, 4, 6, 8 and 10, helical dividers 49 compel fluid A to follow a helical path, longer than a straight path, to ensure that it remains a considerable time in the exchanger, thus producing a more 4- effective exchange of heat. In spaces 1, 3, 5, 7, 9 and 11, helical dividers 50 have the same effect on fluid B.

The helical dividers may be replaced by any device whereby either the turbulence or the length of path of the fluid can be increased; in particular, the cylinders may be made of thin sheet embossed in a check pattern or by any other means by which turbulence can be increased, or the thickness of the films of fluid can be reduced as required.

One of the fluids may follow a single path as described or have several paths. To achieve this, all that is needed is to partition 01f the distribution chambers, that is to say to leave one or more part-cylinders shut oil between partitions 23 and 24 (FIGURE 2).

In FIGURE 3 is seen a small exchanger, the various cylinders of which are introduced into grooves in plates 101 and end plates 102, with packings interposed at 103, without the need for fixing-bolts as in the Preceding case. All the parts of the exchanger are held in place by means of a single axial tie-rod, 104, the ends of which are threaded to take pressure nuts 105. These nuts bear against the small base of a frusto-conical cap 166, which in turn bears against end plates 102, so as to distribute the stresses during tightening.

The various dimensions of the exchanger (thickness of cylinders and plates, number of cylinders, length etc.) must naturally be appropriate to each application considered. Thus, for the exchange of heat between gases, the thickness are appreciably diminished, so that the manufacturing processes are diiferent and simpler. For example, the cylinders can be formed by bending and turning over the sheet metal, while the plates and end plates can be stamped out.

This construction has numerous advantages over existing equipment, as has already been explained, but offers no easy solution to certain particularly diflicult problems involving requirements which are often contradictory. Thus, for very viscous fluids, such as those encountered in sugar refineries, the passages which place the distribution chambers in communication with the annular spaces must be large enough to avoid clogging; but it is advantageous, on the other hand, for these annular spaces to be as narrow as possible if the exchanger is to have a satisfactory performance.

One of the advantages of this heat exchanger lies in the possibility of disassembly for cleaning. However, in the course of handling for dismantling and cleaning, the cylinder ends may be damaged. Now, any irregularity in the cylinder ends is extremely serious, because it is these which bear on the leak-proof packings. As mentioned above, to avoid leaks, it is advisable to true the cylinder ends very time before refitting; and apart from the time that must be spent on this work the length of the cylinders is reduced. Moreover, one single damaged cylinder necessitates the truing of all the others, since they must all inevitably be of equal length.

Compressing the packings in their grooves by means of the cylinder ends has also the disadvantage that contact with the packing is made only over part of its width. It is therefore possible for the packing to be distorted on each side of the cylinder and it may finally even be cut, so that the joint is no longer leakproof.

Reference to FIGURES 4 and 5 will show how these drawbacks may be remedied.

Cylinders 0 have annular rings 60 welded to them, which act as a reinforcement for the said cylinders and at the same time provide a seating for packings 61 compressed between these rings and ridges 13a on plate 13. The fluid passages provided in this plate 13 consist of bores opposite the appropriate spaces, as described above in relation to FIGURE 2.

This construction is particularly advantageous when one is dealing with extremely viscous or very hot e.g. boiler, fluids. In this latter case, indeed, one has to keep the cylinders well apart; and these need to be fairly thick, in view of the risks of corrosion and mechanical stress resulting from the temperature and rate of flow of the fluids.

In FIGURE 5, the exchanger consists of a vertical boiler, the burner of which (not shown) is situated in the upper part along the centre line of the heat exchanger.

Cylinders 0 bear on plates 210 and 211 through rings 60, as can be seen on a large scale in FIGURE 4. The flames which are directed downwardly as indicated by arrow C, reach a smoke-box 264, lined with refractory material or water-jacketed. The hot gases are thereupon distributed through alternate cylinders and are discharged through outlet 203. The water to be heated enters the boiler through inlet 200 and is discharged through outlet 201, having traversed the annular spaces adjacent to those traversed by the hot gases.

In this application it is necessary for the central space containing the burner to be large in size; and in view of the position of this burner it is impossible to fit a central tie-rod. For this reason, the annular space round the central cylinder is a water jacket, through which pass four longitudinal tie-rods 212 (only two of which are visible in the drawing), which are similar in effect to tie-rod 36.

With this construction, the fluids (water and flue gases) flow in the same direction. In the present instance, this has no significant effect on performance, in view of the very high temperature of the gases and the relatively low temperature to which the water is raised.

For this reason, the central cylinder may be made thicker than the others to provide greater resistance to heat stresses.

Whichever form of construction be adopted, the helical dividers (4? and 50, FIGURE 1) may be retained, or alternatively omitted or replaced by other devices, according to the characteristics of the fluids. However, when there are no helical dividers, intermediate members may be fixed to each cylinder to serve as supports for the adjacent cylinders. This provides strength to resist pressure and enables the structure to be more rigid without affecting the flow of fluid.

Referring now to FIGURES 6, 7 and 8, there is shown a form of construction by means of which one cannot only bring the cylinders as close together as desired, but also reduce their thickness, while still retaining the optimum rate of flow of fluid. The passages from the distribution chambers to the annular spaces can still be of adequate dimensions to suit the cross-section of the particular annular spaces. no longer seated on the ends of the cylinder so that these ends may be damaged to some extent without affecting the seal in any way. Finally, each packing is compressed on all four of its faces which makes it considerably more effective.

As will be seen, concentric cylinders 0 have integral extensions 0', the length of which extensions increase towards the centre of the structure and adjacent the ends of which are welded rings 60 for annular packings 61.

The cylindrical casing 62 of each distribution chamber encloses the extensions 0, which are fitted to plates 63, the latter consisting of end rings 64 and 68, the diameter of which decreases away from the end of the structure, the rings being secured to one another to form a step like member. Each end ring has a seating machined on it and against which the packings 61 are pressed by the rings 60.

The width of these seatings, like those of rings 60, is substantially the same as that of the packings 61 in order that these packings may be contacted on all four sides.

The top of plate 63, which is generally frusto-conical in shape, consists of a closure plate 69 having a central hole 70 to enable a longitudinal tie-rod 36 to pass therethrough. This closure plate 69 has a machined internal Furthermore, the packings are 6 seating for receiving the packing 61 on the innermost extension 0'.

Each of the end rings 64 to 68 has a vent 71 to 75, respectively each of which constitutes a passage for the fluid and extends over rather less than half the circumference of the ring to communicate with an annular space. In particular, vent '71 communicates with annular space 2, vent 72 with annular space 3, vent 73 with annular space 4, vent 74 with annular space 5 and vent 75 with annular space 6. The spaces 2, 4 and 6 receive the fluid admitted through inlet 20 and discharged through outlet 22, while spaces 3 and 5 receive the fluid admitted through inlet 19 and discharged through outlet 21.

To keep the two fluids apart at the inlet to these end rings, vents 71 to 75 are formed by a continuous groove in each ring, the vents in adjacent rings being offset 180 on each side of two radial partitions 76 and 77 which are welded in a common plane to the end tubes and closure plates.

The casing 62 is fixed to the end ring 64 and is terminated by a plate 18, the partitions 76 and 77 dividing the interior space in casing 62 into two, the inlet 19 and outlet 22 at one end, and inlet 20 and outlet 21 at the other end lying on opposite sides of the plane containing these partitions.

To the closure plate 69 is fixed an axial collar 80, which extends to the end plate so as to isolate the longitudinal tie-rod 36 from the fluids. This tie-rod 36 is held against the closure plates 69 at each end of the exchanger by nuts 37 and lock-nuts 33, a leak-proof washer being interposed between closure plate 69 and nut 37.

The plate 18 has an axial aperture closed by cover 82 through which the tie-rod 36 passes, the cover being held in place by nuts 39 and 40 screwed on to this tie-rod.

The end ring 64 has a peripheral flange 64a, enabling it to be connected by bolts 83 to a flange 84 welded to the outermost cylinder 0.

Similarly, the casing 62 has a welded flange 85, en-

abling end plates 17 and 18, respectively, to be attached thereto by bolts 86, a seal 87 being interposed between flanges and plates 17 and 18. In this way, the two fluids are kept apart in each distribution chamber by partitions 76 and 77 and reach their respective annular spaces through the end-ring vents.

It should be noted that the frusto-conical shape of plate 63, on which nut 37 bears, distributes the stress in the same way as the caps 106 in FIGURE 3.

Whatever be the spacing between cylinders 0, passages of adequate size can still be provided, since these consist of vents, the height of which is independent of the cylinder spacing. To increase the flow through the vents, in fact, all that is necessary is to recess the end rings more deeply. This is not possible with the aforementioned flat plates 13 and 14, since the fluid passages in these are at right-angles to the annular spaces.

The seatings of the packings are wider than the thickness of the cylinder and the flat packings 61 can therefore be tightened right home. One may even provide shallow grooves on the seatings, so as to achieve a perfeet seal in all circumstances. Since the packings are enclosed on all four sides, they cannot possibly come adrift. A further advantage of this form of construction is that a more adequate fluid-tight seal is formed since the fluid would have to pass round the two faces of the seal.

Cylinders 0 do not need to have their ends machined and they are far less liable to damage; and even if their ends should be damaged in handling, this does not matter since they no longer form part of the seal.

Rings 60 fitted to cylinders 0 or to the extensions 0 thereof, again constitute a reinforcement which enables the cylinders to be made more rigid, yet less thick.

While there have been described what is at present considered to be preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein within the scope of the appended claims without departing from the scope and spirit of the invention.

I claim:

1. In a heat-exchanger for fluids, of the type comprising a plurality of concentric cylinders defining annular spaces among which the fluids are divided in alternating fashion so that every other annular space contains one fluid while the remaining annular spaces contain a second fluid, and a pair of distribution chambers into which these fluids are introduced, and evacuated from, said exchanger, each of said chambers being attached to a respective end of said exchanger and being constituted by an enclosure communicating with an inlet for one of the fluids and an outlet for the other thereof, the improvement comprising: longitudinal extensions of the cylinders of the heat exchanger itself, said extensions being disposed within said enclosure of each chamber; a perforated base associated with the extensions in each said enclosure, and at least in part supporting said extensions such that the latter are disposed in said chambers, said base separating its respective chamber from said heat exchanger and defining a plurality of annular sectors in said chambers, each of which sectors communicates with a respective one of said annular spaces of said heat exchanger, so that a heat exchange is carried out between the fluids from their point of entry to their point of exit from the assembly; and a pair of radial walls cutting said extensions, the circumferential extent of said extensions being defined by said walls, and one of the fluids being introduced into the chamber between said walls.

2. A device as recited in claim It wherein, for each said chamber, said base is flat and is pierced by a plurality of passages which extend at right angles to alternate ones of said annular sectors in the region between said walls and at right angles to all of said annular sectors in the region outside said walls, said walls being interrupted across those ones of said annular sectors having passages placed in the region between said walls.

3. A heat exchanger as recited in claim 2 wherein at least one of said extensions remains unbroken between said radial walls in order to provoke several traverses through the heat exchanger by at least one of said fluids.

4. A heat exchanger as recited in claim 2 wherein each of said cylinders and each of said extensions carries, near its extremities, an exterior welded packing ring which constitutes both a reinforcement for the cylinders and a support for an impermeable packing.

5. A heat exchanger as recited in claim 4 wherein said flat base contains a plurality of concentric grooves, each of which is wider than the thickness of said cylinders and a plurality of concentric ribs between said grooves, said ribs constituting supports for said cylinders, and said passage being arranged in said grooves.

6. A heat exchanger as recited in claim 4- in which the width of said packing rings is substantially equal to that of the packings to be associated therewith so that these packings will be imprisoned between four walls defining a rectangle.

7. A heat exchanger as recited in claim 6 further comprising a tie rod passing within the innermost one of said cylinders, said tie rod being threaded at its extremities for receiving nuts for maintaining said distribution chambers in contact with said heat exchanger itself.

8. A heat exchanger as recited in claim 6 further comprising at least one pair of longitudinally extending tie rods located on diametrically opposed sides of the exterior of the innermost one of said cylinders.

9. A heat exchanger as recited in claim 7 further comprising a frusto-conical cap at each end of said exchanger, each said cap having its large base open and its small base closed by an end piece having a central hole for receiving said tie rod, wherein said large end of each said cap bears against said closing plate at its respective end and said tie rod extends through said holes in said end pieces for receiving threaded nuts for holding said caps against said closing plates.

10. In a heat exchanger for fluids, of the type com prising a plurality of concentric cylinders defining annular spaces among which the fluids are divided in alternating fashion so that every other annular space contains one fluid while the remaining annular spaces contain a second fluid, and a pair of distribution chambers into which these fluids are introduced, and evacuated from, said exchanger, each of said chambers being attached to a respective end of said exchanger and being constituted by an enclosure communicating with an inlet for one of the fluids and an outlet for the other thereof, the improvement comprising: longitudinal extensions of the cylinders of the heat exchanger itself, said extensions being disposed within said enclosure of each chamber; a perforated base associated with the extensions in each said enclosure and at least in part supporting said extensions such that the latter are disposed in said chambers, said base separating its respective chamber from said heat exchanger and defining a plurality of annular sectors in said chambers, each of which sectors communicates with a respective one of said annular spaces of said heat exchanger, so that a heat exchange is carried out between the fluids from their point of entry to their point of exit from the assembly; and a pair of radial walls cutting said extensions, the circumferential extent of said extensions being defined by said walls, and one of the fluids being introduced into the chamber between said walls, said extensions of said cylinders having varying lengths, the longest being at the center of the exchanger and the shortest being at the perimeter thereof, said base in each said enclosure being generally frusto-conical in shape and being pierced by radial passages located at the respective extremities of said extensions.

11. A heat exchanger as recited in claim 10 wherein each of said enclosures is attached to the end of its respective base and comprises a closing frontal plate, and further comprising a radial partition separating the interior of said enclosure into two regions, one of said regions being in communication with said input for one fluid and the other region being in communication with said output for the other fluid, and wherein said passages in said base are alternatively distributed on opposite sides of said partition.

12. A heat exchanger as recited in claim 11 further comprising: a tie rod passing within the innermost one of said cylinders, said tie rod being threaded at its extremities; an axial sleeve for each of said distribution chambers, said sleeve being attached between the outermost end of said base and said frontal closing plate, said plate having an axial opening at its center; and a cover plate for each of said distribution chambers, said cover plate having an axial hole for receiving said tie rod; and wherein said radial partition is composed of two aligned parts which are attached to said base and to said sleeve, and said tie rod passes through said sleeves and, through said hole in said cover plates, to the exterior of said closing plates to permit said cover plates to be maintained against their respective closing plates by means of thread ed nuts screwed into the extremities of said tie rod.

13. A heat exchanger as recited in claim 10 wherein said base is comprised of a plurality of collars of progressively decreasing diameter, each of which is adjacent to, and attached to the next larger collar, and each, except the smallest collar, containing a vent which forms a fluid passage constituted by a continuous slot having an extent equal to or less than the semi-circumference of said collar, the smallest collar being of uniform periphery and contalning an axial hole.

14. A heat exchanger according to claim 10 wherein the bottom of said base carries a flange for attaching it, by means of bolts, to another flange rigidly attached to the outer cylinder of said heat exchanger.

15. A heat exchanger as recited in claim 10 wherein each of said cylinders and each of said extensions carries,

near its extremities, an exterior welded packing ring Whichconstitutes both a reinforcement for the cylinders and a support for an impermeable packing and said frustoconical base comprises a plurality of tiered segments each of which has a support surface at its inner circumference for bearing against said packing whereby said packing will be compressed by its respective packing ring and base support surface.

16. A heat exchanger as recited in claim 10 further comprising a tie rod passing through the innermost one of said cylinders, said tie rod being threaded at its extrcmities for receiving nuts which Will be supported against the exterior surface of the end of each of said bases for maintaining said distribution chambers against the ends of said heat exchanger.

References Cited by the Examiner UNITED STATES PATENTS 826,773 7/06 Engleitner 165--141 2,576,309 11/51 Ruemelin 165--155 X 2,898,384 8/59 Veriot 165-8l X FOREIGN PATENTS 4,832 3/03 Great Britain. 517,989 11/55 Canada.

ROBERT A. OLEARY, Primary Examiner.

CHARLES SUKALO, Examiner. 

1. IN A HEAT-EXCHANGER FOR FLUIDS, OF THE TYPE COMPRISING A PLURALITY OF CONCENTRIC CYLINDERS DEFINING ANNULAR SPACES AMONG WHICH THE FLUIDS ARE DIVIDEN IN ALTERNATING FASHION SO THAT EVERY OTHER ANNULAR SPACE CONTAINS ON FLUID WHILE THE REMAINING ANNULAR SPACES CONTAIN A SECOND FLUID, AND A PAIR OF DISTRIBUTION CHAMBERS INTO WHICH THESE FLUIDS ARE INTRODUCED, AND EVACUATED FROM, SAID EXCHANGER, EACH OF SAID CHAMBERS BEING ATTACHED TO A RESPECTIVE END OF SAID EXCHANGER AND BEING CONSTITUTED BY AN ENCLOSURE COMMUNICATING WITH AN INLET FOR ONE OF THE FLUIDS AND AN OUTLET FOR THE OTHER THEREOF, THE IMPROVEMENT COMPRISING: LONGITUDINAL EXTENDINGS OF THE CYLINDERS OF THE HEAT EXCHANGER ITSELF, SAID EXTENSIONS BEING DISPOSED WITHIN SAID ENCLOSURE OF EACH CHAMBER; A PERFORATED BASE ASSOCIATED WITH THE EXTENSIONS IN EACH SAID ENCLOSURE, AND AT LEAST IN PART SUPPORTING SAID EXTENSIONS SUCH THAT THE LATTER ARE DISPOSED IN SAID CHAMBERS, SAID BASE SEPARATING ITS RESPECTIVE CHAMBER FROM SAID HEAT EXCHANGER AND DEFINING A PLURALITY OF ANNULAR SECTORS IN SAID CHAMBERS, EACH OF WHICH SECTOR COMMUNICATES WITH A RE- 